Sure, they split one two-game set and sit at 1-1 in a three-game series that won’t conclude until next month (due to Minnesota still trying to wriggle free from the frozen grip of winter), but at 8-5 the Mariners are playing some pretty good baseball to start the season.

That being said, they haven’t had a week yet like the one they’re entering.

The defending world champion Houston Astros arrive at Safeco Field on Monday night, and a loss in the four-game series could have a disastrous effect on the momentum the Mariners have built up with their strong start.

Here are three storylines to keep an eye on this week.

When it all clicks.

Last week was a good look at the Mariners’ offense can do, and it sure is impressive. On Saturday night, Seattle hit four home runs and pounded out 17 hits to slug its way past Oakland, marking the fourth time in six games that the Mariners scored at least seven runs – and it should be no surprise that they won each of those four contests.

Here are some fun things to read if you’re a Mariners fan.

• Robinson Cano is second in the American League in average (.375) and second in the majors in on-base percentage (.537).
• Mitch Haniger is tied for the MLB lead in RBIs (15) and is tied for sixth in the AL in homers (four).
• Dee Gordon leads the majors in stolen bases (seven) and had a hit in every game this season until Sunday.
• Gordon and Segura are sporting matching .327 averages and .362 OBPs atop the Mariners’ order.
• Kyle Seager is having the best April of his career, with a .300/.345/.560 slash line, three homers, 11 RBIs and just six strikeouts in 51 plate appearances.
• The Mariners have scored at least five runs in seven games so far, and only two of those came when All-Star designated hitter Nelson Cruz wasn’t on the disabled list.
• Daniel Vogelbach hit his first two MLB home runs in consecutive days, including one that landed above the Hit It Here Cafe at Safeco Field.

Point being, the Mariners’ offense is legitimately good – usually. Seattle was limited to two hits not just once but twice last week. Hopefully it won’t continue to be so drastic with the feast or famine trend going forward.

No. 5 arrives.

Tuesday’s game against the Astros will mark the first time this campaign that the Mariners will need a fifth starter, as scheduled off days and an extra day off due to a postponed game in Minnesota allowed Seattle to make due with just four in their rotation.

That’s been helpful as Erasmo Ramirez has been working his way back from a lat strain suffered in spring training, and the Mariners have been able to carry an extra person either on the bench or in the bullpen as a result. Ramirez won’t be ready for Tuesday’s start, though, so it will be Ariel Miranda to get the call up from Triple-A Tacoma.

Miranda was a stalwart in the rotation last year for the Mariners and had a nice spring training, but the 29-year-old lefty was the odd man out after Ramirez, Mike Leake and Marco Gonzales were all added via trade late last season and penciled in to be behind Felix Hernandez and James Paxton in the 2018 rotation.

If Miranda is looking to show the Mariners he deserves another shot at a full-time gig in the big league rotation, shutting down the Houston’s stacked lineup would probably do the trick.

So … the Astros.

As good as the Mariners have been out of the gate, they still haven’t been as good as the Astros.

Yes, the team that has been a thorn in Seattle’s side pretty much since it joined the AL West is still a half-game ahead of the Mariners entering the series. And to make matters worse, both Houston and Seattle are chasing the Angels, who have received quite the boost from (sorry, M’s fans) two-way phenom Shohei Ohtani.

But back to Houston.

The gang is still all there for the Astros. The 2018 AL MVP, Jose Altuve. The 2018 World Series MVP, George Springer. The 2018 ALCS MVP, Justin Verlander (although he’s not scheduled to start vs. the Mariners in this series). Oh, and don’t forget about 24-year-old All-Star shortstop Carlos Correa or 2015 AL Cy Young Award winner Dallas Kuechel, who is scheduled to start Monday opposite Paxton.

As if that crew wasn’t enough – and clearly it was because they won the World Series – Houston went out and got Gerrit Cole over the offseason, and all he has done is turn into Nolan Ryan, striking out 36 batters in his first three starts (21 innings) in an Astros uniform. The early Cy Young candidate will match up against Leake on Wednesday, by the way.

So let’s look on the bright side. If the Mariners come away with two wins against Houston, it’s a good sign. If they win three, it sends a message. If they sweep the Astros, well, there will be a team from Seattle getting significant national attention on Friday morning.